fig4

Figure 4. (A) Schematic illustration of the fabrication process of Ni-doped nanoporous graphene; Reproduced from Ref.^[51] with permission from Wiley-VCH. (B) Schematic illustration of the fabrication of Fe SACs; (C) Enlarged HAADF-STEM image of Fe-N-SCCFs. Reproduced from Ref.^[52] with permission from the American Chemical Society. Scheme for the construction of high-loading single-atom Pd1/PCN with chemical scissors. (D and H) The models of PCN, (E and I) The models of Pdh/PCN, (F and J) The schemes of selective etching; (G and K) As-synthesized Pd1/PCN. Only bonds between Pd and PCN have remained. (L) Recycling Pd to avoid waste. Reproduced from Ref.^[53] with permission from Wiley-VCH.